Fig. 20. Another cast of the interior of a cranidium found with 

 the preceding two specimens, X 8, more doubtfully referred 

 to this species. This has been greatly shortened by pres- 

 sure and is otherwise imperfect. It is figured mainly be- 

 cause it retains most of the anterior border and shows the 

 separateness of the median pair of spines even in this 

 form, in which their bases are very close to the anterior 

 ends of the facial sutures. U.S.N. M. No. 80547b. 

 21. A pygidium found with the preceding, X 8. Though 

 somewhat shortened by compression, it still shows a 

 greater width of border than is found in other species. 

 In general it reminds most of the pygidium assigned to 

 T. impundatus. U.S.N.M. No. 80547c. 

 AU found with T. buttsi in the basal part of the Athens shale, 

 1.5 miles northeast of Longview, Ala. 



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